Another valve check problem

[markjenn]

It would be surprising to me if Yamaha were using a "waste squirt" from the injectors similarly to a waste spark. Any kind of wast squirt would seem to have quite negative effect on both fuel mileage and emissions.

You'd think so, but I recall reading a while back that throttle-body fuel injection systems are quite insensitive to injection timing. You can spray fuel in almost anytime you please and it is so turbulent that even if it is deposited on the walls of the inlet tract, it evaporates and is well-atomized when it makes it to the combustion chamber.

And fuel injectors don't inject all their fuel in a momentary burst - they stay open for some period of time with duration determining mixture - this duration (called pulse width) may be fairly big compared to the total time of the four-stroke cycle. (I recall reading that injector pulse width may be up to 85% of the total cycle time for high-RPM/full-throttle situations; in this case the injector would be delivering fuel 85% of the time and would be delivering across all the four-stroke cycles.) So the idea that fuel injection is a quick/short injection right into the combustion chamber is more apt to direct-injection, not to throttle-body injection. Throttle body injection is, in some ways, more similar to a carb than a direct injection and obviously carbs have no timing with respect to intake valve opening.

Anyone following this might find this discussion interesting - it indicates there are a wide variety of approaches to timing of fuel injection.

http://mdhmotors.com/fuel-and-air-induction-systems-diagnosis/

- Mark

 

[OldRider]

Sounds like the quote is from a patent application.

While it is certainly possible Yamaha is using something like this, I doubt the sensor provided in the S10 would be suitable - you'd probably need to have a sensor in the actual inlet tract of each cylinder, not something in the airbox. I think the S10's sensor is mainly to trim the fuel injection settings for air density and has nothing to do with trying to figure out the timing of intake valve opening. Could be wrong.

- Mark

Found this:

"One sensor, the camshaft position sensor, provides a very interesting and important chore. Since the four-stroke engine's crankshaft rotates twice per power cycle, the ECU has no way to tell, from the crankshaft sensor's information alone, the engine's compression stroke from its exhaust stroke. -- they're both upward strokes and to the crankshaft sensor, there is no difference. The camshaft position sensor adds half-speed information to the mix to divide the crankshaft's data by two, and thus provides the necessary distinction. Some fuel injected vehicles use the intake air pressure sensor instead of a cam position sensor, with the ECU being programmed to count the number of degrees between the intake and compression stroke. A simpler, less expensive system. "

http://www.motorcycleproject.com/text/fuel_injection_pt2.html

 

[OldRider]

This is from 2010 and note 16 shows that Yamaha used intake air pressure instead of a cam position sensor even back then, so you set the cams with the crank on the K mark and the ECU takes over from there.

 

[snakebitten]

Incredible thread with an amazing accumulated knowledge.
And although I read it with intentional focus, I choose to not waste any of my precious remaining brain cells to store it.
Or put another way, it's too painful and frightening to hold myself accountable for any of this.
Sometimes I'll just write the check.

Again, yaw amaze me.

 

[Fatallybitten]

I will echo Snakebitten's comments. I am grateful to everyone who has shared their knowledge of motorcycle engines in general and the S10 in particular. I have re-installed and timed the cams, did a final check of valve clearances (since that was what this was all about) and I am about to re-install the valve cover. I can already see that the gasket is going to be a pain.

 

[Pterodactyl]

I will echo Snakebitten's comments. I am grateful to everyone who has shared their knowledge of motorcycle engines in general and the S10 in particular. I have re-installed and timed the cams, did a final check of valve clearances (since that was what this was all about) and I am about to re-install the valve cover. I can already see that the gasket is going to be a pain.

Congratulations! I realize my earlier responses were overly pissy, negative and ultimately wrong; I regret making them. I'm glad you were able to resolve your situation with input some of the more knowledgable folks on the forum. Good work!

 

[Juan]

I will echo Snakebitten's comments. I am grateful to everyone who has shared their knowledge of motorcycle engines in general and the S10 in particular. I have re-installed and timed the cams, did a final check of valve clearances (since that was what this was all about) and I am about to re-install the valve cover. I can already see that the gasket is going to be a pain.

Good Lord - This subject has become very technical. Though I do have limited technical knowledge, I surely would not embark on anything this complicated. I admire all those who persevere and end up satisfied of a task successfully completed.

 

[Fatallybitten]

The bike fired right up! Thanks to everyone for the help. Now I just need to wait a couple months until spring to take it for a spin. I am in the great white north, which is currently living up to its reputation.

 

[BWC]

Excellent news!
Thanks to your percervience, and some good input from others we now have a better understanding of Yamahas 270 degree twin. ::008::

 

[WJBertrand]

Congrats, I'm reading with interest as I'm about to dive into this job this coming weekend.


Sent from my iPhone using Tapatalk

 

[RED CAT]

Way to go Dave! I will certainly be coming to you for any technical info in the future. How about changing that fork oil now on that ES. Decided to leave mine alone. Too complicated for an old guy. Going to bleed the brakes and clutch next. Too damn cold.

 

[Checkswrecks]

Congrats to Fatallybitten and a nod of respect to Pterodactyl.
::012:: ::012::

 

[Fatallybitten]

Congratulations! I realize my earlier responses were overly pissy, negative and ultimately wrong; I regret making them. I'm glad you were able to resolve your situation with input some of the more knowledgable folks on the forum. Good work!

Pterodactyl, you may have been right with your comments, but I am a persistent fellow and, so far, I have been able to overcome my technical shortcomings with lots of help from people on MC forums. The S10 forum is a great community! BTW, no harm no foul on your comments. I could easily have ended up having to do exactly as you were suggesting. Cheers.

 

[Fatallybitten]

And one more tip for those who are going to do this for the first time. The valve cover gasket was the most difficult part of putting the bike back together. It didn't help that the gasket I got from the dealer was kinked in some of the wrong places and wouldn't stay where it was supposed to be. The tip is to do the blow test through the breather hose. It is a sure fire way of knowing you have the gasket on and properly sealed in all the difficult areas to get at. Just make sure you have put the crank case cover back on first or you, like me, will be looking for leaks in the gasket until you clue in that there is still a big hole in the engine!

 

[markjenn]

This is from 2010 and note 16 shows that Yamaha used intake air pressure instead of a cam position sensor even back then, so you set the cams with the crank on the K mark and the ECU takes over from there.

Good research!!! Nice find. Still like to have confirmation of this approach for the S10 specifically, but it makes some sense.

- Mark

 

[RonH]

Good job and glad it all worked out. Another tip is to not replace the valve cover gasket unless necessary. Be sure to keep the gasket attached to the cover and remove the cover and gasket together. Still not a simple procedure guiding all 4 end plugs properly into place while reinstalling the cover, but once the cover and
gasket are separated to replace the gasket it is a rough job to keep the gasket in the correct position to reinstall the cover. I know most believe in replacing gaskets every time, but the new rubber gaskets can be reused and makes the job a little easier.